Diagnostic Key Tips for Limiting Off-Characters Arising during Wine Maturation and Storage
Tips for Limiting Off-Characters Arising during Wine Maturation and Storage
- Since removal of post-fermentation off-characters is challenging the best strategy is to prevent their formation. Sound sanitation practices should be employed in the winery and barrels that have evidence of infection should be scrupulously cleaned and sanitized and perhaps removed from use in production.
- Opportunities for cross-contamination should be limited. Biofilms can form on any surface in the winery including and especially hoses. Large dimension hoses are often difficult to handle and sanitize (akin to wrestling an anaconda) and can therefore be a source of contamination of sound wines. The winery is only as clean as its weakest component.
- Wines in storage should be checked periodically for the appearance of off odors. All winery personnel should be trained in what the undesired odors are and protocols put in place for isolation and treatment of infected lots of wine.
- Do not top off sound barrels with an odd-smelling wine thinking the negative aromatic compound will be diluted. If it is due to microbial activity the sound wine has just been inoculated with a spoilage organism.
- Monitor SO2 levels. Free SO2 levels should be in the inhibitory range for the microorganisms that may pose a spoilage problem. Generally microbes are sensitive to SO2 in the low ppm range so a free SO2 of 10 ppm will be sufficient. However SO2-resistant forms of most spoilage yeasts and bacteria are known so this may not always solve the problem. The level of free SO2 is a function of pH and high pH wines may be particularly at risk of spoilage. To avoid spoilage pH may have to be adjusted and decreased.
- Sterile filtration can remove spoilage organisms but it is important to do this in a way that does not spread the infection and making sure the vessels used to contain the wine are also thoroughly cleaned and sanitized to remove any potential biofilm.
- Keeping fruit flies, ants and other insects to a minimum in the winery will decrease chances of spoilage of wines. Fruit flies in particular are attracted to ethyl acetate and other esters produced by microbial activity and will then visit sound wines and deposit microbes. They will also visit open bags of fining agents so it is important to keep all materials added to the wine free from insect infestation.